Li-Fraumeni syndrome (LFS) is a clinically and genetically heterogeneous inherited cancer syndrome. Most[unreadable] cases (approximately 70%) identified and characterized to date are associated with dominant germline mutations in the[unreadable] tumor suppressor gene TP53 (p53). Another tumor suppressor gene, CHEK2, was recently identified as a[unreadable] second minor predisposing locus. Studying a series of non-p53 LFS kindreds, we have shown that there is[unreadable] additional genetic heterogeneity in LFS kindreds with inherited predisposition at a locus other than p53 or[unreadable] CHEK2. Using a genome-wide scan for linkage with complementing parametric and non-parametric analysis[unreadable] methods, we have identified linkage to a separate, previously not implicated genomic region. In addition to a[unreadable] major predisposing locus, there is evidence for significant heterogeneity in risk within and between kindreds,[unreadable] in both p53 and non-p53 LFS kindreds. These data implicate additional risk modifiers in the genesis of LFS[unreadable] and its variants, including another major gene(s) as well as modifier genes. We hypothesize that the[unreadable] inherited susceptibility to childhood and associated cancers in non-p53, similar to p53, LFS kindreds[unreadable] is the result of a highly penetrant, dominantly acting gene. In keeping with a multi-step carcinogenesis[unreadable] model, however, germline mutations are not sufficient, and other modifier genes and factors,[unreadable] including epigenetic alterations, appear to be necessary in both p53 and non-p53 LFS kindreds. To[unreadable] test these hypotheses, we propose the following three specific aims that take advantage of the unique and[unreadable] large resources assembled as part of this program project: (1) to identify and characterize the gene for the[unreadable] newly mapped non-p53 LFS susceptibility locus; (2) to identify p53 and non-p53 LFS modifier genes;[unreadable] and (3) to evaluate the contribution of promoter hypermethylation and transcriptional inactivation of[unreadable] known cancer genes subject to epigenetic silencing to the LFS phenotype. Identification of the major[unreadable] non-p53 predisposing gene and its underlying mutations should provide insight into other genetic events that[unreadable] predispose to the genesis of diverse tumor types associated with LFS and its variants. Our integrated[unreadable] genomics approach that combines genomic and transcriptomic with epigenomic profiling will yield a better[unreadable] understanding of the complex molecular genetic and epigenetic events underlying the multi-step[unreadable] carcinogenesis in LFS and its variants and will provide valuable functional clues about potential candidate[unreadable] cancer and modifier genes, complex cellular candidate pathways, and the overall pathophysiology. As a[unreadable] childhood cancer, LFS is a unique model to study the underlying genetic events associated with a complex[unreadable] cancer syndrome, presumably because fewer such alterations are needed to give rise to the associated[unreadable] cancer. Similar to p53, other LFS predisposition and/or modifier genes may be functionally similarly important[unreadable] in other solid tumor types lacking a clear predisposition and inheritance pattern.